1. Technical Field
The present invention relates to a. discharge lamp, a method for producing the discharge lamp, a light source device, and a projector.
2. Related Art
Conventionally, projectors are used in a variety of application areas including image projectors for presentations in meetings and home theater systems in homes. Most of the projectors incorporate a light source device such as a discharge lamp having electrodes. For example, the discharge lamp is a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp.
On the other hand, the discharge lamp causes an increase in temperature when the lamp is in its on state. Thereby, there occurs devitrification due to crystallization of quartz glass used as a material of an arc tube, resulting in a reduction in transmitted light or a decrease in strength of the arc tube itself. In order to solve the problems, for example, as in JP-A-2008-270074, an yttrium oxide (Y2O3) film is formed on an inner surface of an arc tube or a hafnium oxide (HfO2) film is formed to prevent crystallization of quartz.
However, the yttrium oxide film has low transmittance and is sintered when exposed to high temperature for a long time. In addition, the hafnium oxide film tends to absorb oxygen and thus is easily oxidized, whereby devitrification can occur. Accordingly, forming only such a monolayer film is not enough to sufficiently obtain a devitrification prevention effect. Thus, further improvement is needed.